OP ARTS AND SCIENCES. 367 



» 

 of chloride of barium with more than two equivalents of cyanide of 

 mercury, and that the analyses were made upon mixtures of the two 

 salts. But the existence of such a body has never been shown, nor do 

 we know an instance of a chloride, iodide, or bromide combining with 

 cyanide of mercury in any other proportion than one equivalent to 

 two. The salts of chloride of nickel and chloride of cobalt which I 

 have mentioned, and a salt said, also on the authority of Poggiale, to 

 be composed of 



2 NH,C1, HgCy, 



are the only exceptions to this statement which I have been able to 

 find. In other instances, as in that of the subjoined analysis, which 

 was made upon large, perfectly defined, and carefully chosen ciystals, 

 deposited by spontaneous evaporation from a liquid containing a con- 

 siderable excess of chloride of barium, such an explanation seems to 

 me entirely inadmissible. The analysis gave 



A direct determination of the water upon another portion gave 6 HO 



=: 11.63. 



The above is one of thirteen analyses of this salt, and is chosen 

 for no other reason than that the crystals were carefully selected, 

 and that its accuracy is vouched for by the agreement of the direct 

 determination of the water with the determination by difference. The 

 water was determined directly in two other cases, and the variation 

 from the determination by difference found to be less than one tenth 

 of one per cent. To control still further the exactness of the analyses 

 and the purity of the double salt, the chlorine was in one instance de- 

 termined ; the analysis gave 7.98, the quantity required by the barium 

 present was 8.01. The cyanide of mercury used was also analyzed by 

 the same process, and with the addition of the same reagents which 

 had been employed in the analysis of the double salt ; the result dif- 

 fered from the calculated composition only by one in the hundredths of 

 a per cent. In all the analyses the deviation from the composition 

 of the theoretical or normal salt is unmistakable, and is the more 



